Method for making aqueous solutions of unsaturated quaternary ammonium salts

Abstract

The present invention relates to a process for the manufacture of aqueous solutions of unsaturated quaternary ammonium salts. The salts can correspond to the following formula (I): in which R represents a methyl or benzyl radical, by reaction, in the presence of water, of N,N-dimethyl-amninoethyl acrylate (DAMEA) with a quaternizing agent of formula (II): R—Cl  (II) in which R is as defined above. Generally, the reaction is carried out in a closed reactor, which includes all the DAMEA and has been pressurized by air or depleted air to 0.5 to 3 bar, by continuously introducing, at a temperature of 35 to 65° C., the quatenlizing agent (II) and the water, until a concentration of salt (I) in the water is obtained. The water starts to be introduced beginning when 0-20% of the amount by weight of the quaternizing agent (II) necessary for the reaction has been added and it being possible for the pressure at the end of the reaction to reach 9 bar. Next, the reactor can be depressurized while keeping the oxygen content constant by simultaneous introduction of air and, after returning to atmospheric pressure, the residual quaternizing agent may be removed.

What is claimed is:  
     
       1. A process for the manufacture of aqueous solutions of unsaturated quaternary ammonium salts corresponding to the following formula (I):                    
       in which R represents a methyl or benzyl radical, by reaction, in the presence of water, of N,N-dimethyl-aminoethyl acrylate (DAMEA) with a quaternizing agent of formula (II):  
       
         
           R—Cl  (II)  
         
       
        in which R is as defined above,  
       (a) the reaction is carried out in a closed reactor, which comprises all the DAMEA and which has been pressurized by air or depleted air to 0.5 to 3 bar, by continuously introducing, at a temperature of 35 to 65° C., the quatemizing agent (II) and the water, until a concentration of salt (I) in the water is obtained, the start of the introduction of the water beginning when 0-20% of the amount by weight of the quaternizing agent (II) necessary for the reaction has been added and it being possible for the pressure at the end of the reaction to reach 9 bar; then  
       (b) the reactor is depressurized while keeping the oxygen content constant by simultaneous introduction of air and, after returning to atmospheric pressure, the residual quaternizing agent is removed.  
     
     
       2. The process as claimed in  claim 1 , wherein the reaction is carried out at a temperature of 40 to 60° C. 
     
     
       3. The process as claimed in  claim 1 , wherein the reaction is carried out with a pressure which, at the end of the reaction, reaches 4 to 7 bar. 
     
     
       4. The process as claimed in  claim 1 , wherein the introduction of the water is started when 5-15% of the amount by weight of the quaternizing agent (II) necessary for the reaction has been added. 
     
     
       5. The process as claimed in  claim 1 , wherein the quaternizing agent is introduced over a period of time of 1-7 hours and the water is introduced over a period of time of 2-8 hours. 
     
     
       6. The process as claimed in  claim 1 , wherein the reaction is carried out with a molar ratio of the quaternizing agent to the DAMEA of 1 to 1.1. 
     
     
       7. The process according to  claim 1 , wherein the reaction is carried out with a mean ratio of water/quaternizing agent throughput of 0.1-1.2. 
     
     
       8. The process as claimed in  claim 1 , resulting in an aqueous solution having a concentration of quaternary salts (I) of 50 to 85% by weight. 
     
     
       9. The process as claimed in  claim 1  carried out in the presence of at least one stabilizer which is 3,5-di(tert-butyl)-4-hydroxytoluene, hydroquinone methyl ether, hydroquinone, catechol, tert-butylcatechol, phenothiazine or mixtures of these stabilizers, the content of stabilizing agent(s) being from 20 to 2000 ppm with respect to the aqueous solution of quaternary salt (I). 
     
     
       10. The process as claimed in  claim 9 , carried out in the presence in addition of at least one sequestering agent for metals which is diethylene-triaminepentaacetic acid, the pentasodium salt of diethylenetriaminepentaacetic acid, N-(hydroxyethyl)-ethylenediaminetriacetic acid or the trisodium salt of N-(hydroxyethyl)ethylenediaminetriacetic acid, the content of sequestering agent(s) being 1 to 100 ppm, with respect to the aqueous solution of quaternary salt (I). 
     
     
       11. The process as claimed in  claim 1 , wherein residual quaternizing agent is removed by stripping with air. 
     
     
       12. The process as claimed in  claim 1 , wherein the reaction is carried out with a molar ratio of the quatemizing agent to the DAMEA of 1 to 1.05. 
     
     
       13. The process according to  claim 1 , wherein the reaction is carried out with a mean ratio of water/quaternizing agent throughput of 0.3-0.8. 
     
     
       14. The process as claimed in  claim 1  carried out in the presence of at least one stabilizer which is 3,5-di(tert-butyl)-4-hydroxytoluene, hydroquinone methyl ether, hydroquinone, catechol, tert-butylcatechol, phenothiazine or mixtures of these stabilizers, the content of stabilizing agent(s) being 100 to 1200 ppm, with respect to the aqueous solution of quaternary salt (I). 
     
     
       15. The process as claimed in  claim 9 , carried out in the presence in addition of at least one sequestering agent for metals which is diethylene-triaminepentaacetic acid, the pentasodium salt of diethylenetriaminepentaacetic acid, N-(hydroxyethyl)-ethylenediaminetriacetic acid or the trisodium salt of N-(hydroxyethyl)ethylenediaminetriacetic acid, the content of sequestering agent(s) being 5 to 30 ppm, with respect to the aqueous solution of quaternary salt (I).